Preheat oven to 350°F. Grease a 9x13 inch baking dish.
Cook macaroni according to package instructions, drain, and set aside.
In a medium saucepan, melt vegan butter over medium heat. Add flour and whisk until smooth.
Gradually add vegan milk, whisking constantly until thickened. Add salt, garlic powder, pepper, nutritional yeast flakes and lemon juice and stir until combined.
Remove from heat and stir in cooked macaroni.
Pour into prepared baking dish and bake for 25 minutes or until golden brown.